feat(twitter_threads): download_media.py — stdlib urllib + idempotent + typed per-kind naming

media_names_for_post derives <post_id>_<kind><index>.<ext> (img/vid/gif, per-kind counters) from media_urls; download_media(thread, output_dir) -> Result[list[Path]] downloads via stdlib urlopen, idempotent skip when target exists with size>0, URLError -> Result.err(HttpError). Authorized HTTP-boundary mock tests. TDD: red(no module) -> green(6 media + 16 regression pass).

scripts/twitter_threads/download_media.py

@@ -0,0 +1,56 @@
+"""Download media URLs from ThreadData via stdlib urllib into a local directory."""
+from __future__ import annotations
+from pathlib import Path
+from urllib.request import urlopen
+from urllib.error import URLError
+from urllib.parse import urlparse, parse_qs
+from scripts.twitter_threads.error_types import ErrorInfo, make_error, Result, PostData, ThreadData
+
+def _classify(url: str) -> tuple[str, str]:
+ parsed = urlparse(url)
+ path = parsed.path
+ if "video.twimg.com" in parsed.netloc or path.endswith(".mp4"):
+  if "tweet_video" in path:
+   return ("gif", "mp4")
+  return ("vid", "mp4")
+ qs = parse_qs(parsed.query)
+ fmt = qs.get("format", [""])[0]
+ if fmt:
+  return ("img", fmt)
+ if "." in path:
+  return ("img", path.rsplit(".", 1)[-1])
+ return ("img", "jpg")
+
+def media_names_for_post(post: PostData) -> list[str]:
+ counters: dict[str, int] = {}
+ names: list[str] = []
+ for url in post.media_urls:
+  kind, ext = _classify(url)
+  counters[kind] = counters.get(kind, 0) + 1
+  names.append(f"{post.post_id}_{kind}{counters[kind]}.{ext}")
+ return names
+
+def download_media(thread: ThreadData, output_dir: Path) -> Result[list[Path]]:
+ try:
+  output_dir.mkdir(parents=True, exist_ok=True)
+ except OSError as e:
+  return Result.err(make_error("WriteError", "download_media", str(e)))
+ paths: list[Path] = []
+ for post in thread.posts:
+  names = media_names_for_post(post)
+  for url, name in zip(post.media_urls, names):
+   target = output_dir / name
+   if target.exists() and target.stat().st_size > 0:
+    paths.append(target)
+    continue
+   try:
+    with urlopen(url) as resp:
+     data = resp.read()
+   except URLError as e:
+    return Result.err(make_error("HttpError", "download_media", str(e)))
+   try:
+    target.write_bytes(data)
+   except OSError as e:
+    return Result.err(make_error("WriteError", "download_media", str(e)))
+   paths.append(target)
+ return Result.ok(paths)